A wide variety of mufflers, silencers and snubbers have been devised to minimize the noise otherwise resulting from the direct exposure of pulsating flowing gases to the atmosphere. The treatment of such gas streams is limited by the necessity of avoiding adverse effects on the apparatus into which or from which the streams flow. The apparatus of U.S. Pat. No. 2,562,101 is an example of a reasonably effective unit which, by reason of the straight-through flow path of the gas stream, creates a minimum of resistance to the flow so that the effect on the operation and efficiency of the equipment involved is minimal. Because the effectiveness of this type of snubber depends upon the length of the snubbing chamber with respect to the frequency of the sound to be absorbed, it should be designed, for greatest efficiency, to meet the requirements of the frequency content of a particular application. Better sound absorbing operation is obtained when this length is one-quarter of the wave length of the sound to be attenuated and poorest performance results when this length is one-half of the wave length of the sound. Thus, a particular unit is somewhat selective and limited performancewise.
The object of the present invention is to provide a noise attenuating snubber of the type described which, for a given unit, is effective over a broader range of sound frequencies. More specifically, the object is to provide such apparatus wherein the snubbing or surge chamber is filled with acoustically penetrable media and the gas flow communication with the chamber is provided by a relatively large opening at the upstream end thereof and by the perforations of the gas flow tube which interiorly defines the chamber to achieve a noise attenuating unit which is effective over a relatively broad range of frequencies.
A further object is to provide means for removing entrained moisture from the gases which flow into the surge chamber in order to maintain the acoustic effectiveness of the media and thus of the chamber and unit.